1. Field of the Invention
The present invention relates to a tool exchanging system for an NC machining tool and, more particularly, contemplates to improve the efficiency of the tool exchange thereby to shorten the standby time of the machining tool.
2. Description of the Prior Art
Before entering into the detailed description of the present invention, cursory review of the prior art will be made with reference to FIG. 1 in the accompanying drawings.
A machining tool 1 to which the present invention is to be applied is of the type, in which a workpiece W placed on a table 2 is machined by means of a tool T clamped by a spindle head S and in which the spindle head S is moved in various direction in accordance with the movement of the tool T. Machining tools provided with a tool storage magazine are disclosed in U.S. Pat. Nos. 3,998,338 and 4,238,034. On the other hand, the NC machining tool 1 has its body 3 equipped with a tool column 4, which is stored in advance with tools to be exchanged, so that the tools are exchanged between the column 4 and the spindle head S by the action of a tool exchanging robot 5 attached to the body 3. As a result, the column 4 has its tool exchanging position 6 fixed relative to the body 3. Therefore, the column 4 is moved in accordance with the movement of the spindle head S. On the other hand, the feed of that column 4 with the tools is conducted by carrying a tool magazine M, which is set in advance with a plurality of tools, on a transfer truck to the back of the machining tool 1. If the column 4 is moved during the machining operation, as has been described in the above, the tool exchange between the fixed tool magazine M and the column 4 is impossible. According to the prior art, therefore, the tool exchange is carried out by selecting the timing, at which the spindle head is stopped, such as the workpiece exchanging operation. In recent years, however, the workpiece exchange is advanced in automation so that the time therefore is remarkably shortened, whereas it takes much time to exchange many tools. As a result, the spindle head cannot be moved exclusively for the tool exchange to invite a disadvantage that the machining efficiency is deteriorated.